| 摘要 |
The screw (11) has a thread pilot (22) located in a free region (15) of a shaft (12), and multiple recesses (31) provided in a thread (21), and opening radially outwardly. Each recess has two limiting walls respectively located near the thread pilot, and far from the thread pilot. Multiple cutting bodies (26) are formed with a material having hardness greater than hardness of the thread, and are located in the recesses. An outer surface is surrounded along an axis, and multiple generatices of a flat bearing section in each recess are extended substantially along the thread. |
